This invention relates generally to cleansing bars, and more particularly to cleansing bars having high levels of emollient.
Synthetic detergent or syndet toilet bars have found considerable use as mild cleansing bars but such bars have the potential to be soft and typically require structuring agents to be added to firm or harden the bar. Thus the main function of prior art structurants such as sodium stearate in syndet bars is to provide body and give structure to the product. For example, sodium stearate finds considerable use as a structurant or structuring agent in syndet bar formulations, forming a fibrous network structure which helps in improving the mush and rate of wear properties of the bars. However, there is a problem in structuring syndet bars containing high levels of emollients that are liquid at room temperature (25 C.).
12-Hydroxystearic acid has been previously employed as a strucuturing agent in high water content soap or syndet bars; see e.g. U.S. Pat. No. 5,225,097 issued to M. Kacher, et al. on Jul. 6, 1993 and U.S. Pat. No. 5,227,086 issued to M. Kacher, et al. on Jul. 13,1993; which are herein incorporated by reference. However the bars described by Kacher did not contain high levels of hydrophobic or hydrophilic emollients which have melting points below 25 C. J P Kokai publication no. 7034100A, issued to E. Yoshiyuki, et al. on Feb. 3,1995 describes a syndet bar containing 1 to 30% by weight of a liquid or semi-solid oil and 0.01 to 5% by weight of 12-hydroxystearic acid. However, the physical properties of the bars described by Yoshiyuki are not commercially acceptable, especially regarding the bar""s wear rate and mush properties.
Unexpectedly the use of 12-hydroxystearic acid in syndet formulations at levels in excess of 5% by weight and with high levels of emollients that are liquid at room temperature (i.e. have a melting point below 25 C.) has been found to substantially improve the rate of wear and mush propensity of syndet toilet bars. High rates of wear and mush propensity are negative attributes of prior art syndet formulations as discussed above.
Furthermore it was unexpectedly discovered that the use of 12-hydroxy stearic acid in a low viscosity melt (Brookfield viscosity range of about 10 cps to about 40,000 cps) with high amounts of emollients which are liquid at room temperature gave a relatively stable melt, with no observable phase separation, between 70xc2x0 C. and 110xc2x0 C. with continuous mixing. In comparison, the same quantity of stearic acid as the sole structuring agent yields a very unstable syndet bar system where the hydrophobic emollient phase noticeably separates from the mix in the absence of phase stabilizers such as lauryl alcohol, or alternatively produces an undesirably soft bar in the absence of phase separation. It was also unexpectedly found that the use of 12-hydroxystearic acid in syndet formulations will improve the rate of wear and mush propensity of the formulations.
In one aspect, the present invention relates to a mild toilet bar with high levels of hydrophobic or hydrophilic emollients have a melting point below 25 C. and having 12-hydroxystearic acid as one of its structuring agents at a level above 5% by weight. Preferably, 12-hydroxystearic acid is the primary structuring agent present. Most preferably, 12-hydroxystearic acid is the sole structuring agent present.
Conventional structuring agents preferably are present in the inventive bar in the concentration range of about 5 to about 30% by weight. In the case where 12-hydroxystearic acid is the sole structuring agent, it is present in the concentration range of about 10 to 15%, preferably about 13 to 15% by weight.
In another aspect, the inventive toilet bar is mildly acidic to neutral having a pH range of about 5.0 to 7.0, preferably 5.0 to 6.0, and most preferably 5.3 to 5.7.
In a further aspect, the inventive toilet bar has a low moisture content, in the range of about 1 to less than about 15% by weight of water; preferably in the range of about 2 to about 13% by weight of water, and most preferably in the range of about 2 to about 6% by weight of water.